All lawns will develop weeds at regular intervals, and one important rule needs to be followed whenever spraying for any lawn weeds, which is to ensure we do not spray lawns too close before the next lawn mowing or too soon after the last lawn mowing.
We should never spray for lawn weeds less than one week prior to the next lawn mowing service.
Likewise, once we have sprayed, we want to stop lawn mowing for one week after weed spraying.
Spraying Pesticides Too Close Before Next Lawn Mowing
The reason for waiting one week after spraying and before mowing is that if we were to spray for lawn weeds one day, and then mow the lawn the next day, we would be removing most of the weed herbicide which we had just applied to the lawn, with that same lawn mowing - meaning that we would be removing the leaves of the weeds that contained that same herbicide, and thus removing much of the herbicide itself from the weeds, and stopping the herbicide from working effectively.
By mowing the lawn too soon after applying herbicides we are then removing that same pesticide before it had a chance to be taken into the lawn or weeds.
So the end result will either be no result at all of controling whatever weed problem we were having, or the result would be extremely minor or negligible at best. We have essentially wasted our time and money for no results.
Wait at least one week after spraying - before doing the next lawn mowing.
Spraying Pesticides Too Soon After Last Lawn Mowing
After mowing a lawn, we have left open cuts / wounds on every blade of grass over the lawn, which the grass then requires time to repair from. It will usually take a few days to a week for lawns to seal off the cuts in the blades of grass left from lawn mowing.
If we sprayed for weeds in this time when the wounds of the blades of grass are still open from the last lawn mowing, then the absorption of the pesticide, most especially a weed herbicide, will be directly taken up by the lawn itself through these wounds at a tremendously greater rate.
So instead of the lawn withstanding and resisting against the herbicide treatment, the lawn can very quickly fall victim to that same herbicide meant only for weeds, and the lawn can suffer severe health problems, stress, or even death, very quickly after the application of a herbicide while the blades of grass still have freshly cut wounds from lawn mowing.
We need to allow the lawn enough time to heal itself and to seal off the wounds left from mowing, before we ever do any type of herbicide or pesticide spraying of any kind.
The most generally accepted, and practiced, and easy to remember system for all lawn spraying is:
NEVER spray lawns one before or one week after lawn mowing.
As always, the most effective systems and practices, are always the simplest.